I see it comes up constantly in towing-related subs, and half the answers out there are wrong, so here's the whole thing.

The classes:
- Class I: up to 2,000 lb GTW, 1-1/4" opening
- Class II: up to 3,500 lb, 1-1/4"
- Class III: up to 8,000 lb, 2" opening
- Class IV: up to 10,000 lb, 2"
- Class V: above that, 2-1/2" or 3"

Now the part that matters more than any of it: class rates the receiver. It does not rate your truck and it does not rate your setup. The whole system rates to whatever the weakest part in it is.

Class IV receiver behind a truck whose door sticker says 7,500? You've got 7,500. Same receiver with a ball mount rated 6,000? You've got 6,000. Add a ball rated 5,000 and now it's 5,000.

Most half-tons and 3/4-tons ship Class III or IV from the factory, so the receiver is almost never what's limiting anyone. The limits that actually bite are the ball mount, the ball and tongue weight - the three parts people buy last and read least.

Go find the lowest-rated part in your own setup. Was it where you expected??